In Vivo Gene Therapy Activates Brain Stem Cells

Using customized nanoparticles that they developed, University at Buffalo scientists have for the first time delivered genes into the brains of living mice with an efficiency that is similar to, or better than, viral vectors and with no observable toxic effect.

Nanoparticles developed at UB allow cells on the floor of a mouse brain ventricle to express the gene for green fluorescent protein.

The scientists used gene-nanoparticle complexes to activate adult brain stem/progenitor cells in vivo, demonstrating that it may be possible to "turn on" these otherwise idle cells as effective replacements for those destroyed by neurodegenerative diseases, such as Parkinson's.

A mouse neuron expresses green fluorescent protein gene delivered by the nanoparticles developed at UB.

In addition to delivering therapeutic genes to repair malfunctioning brain cells, the nanoparticles also provide promising models for studying the genetic mechanisms of brain disease.

Viral vectors for gene therapy always carry with them the potential to revert back to wild-type, and some human trials have even resulted in fatalities. As a result, new research focuses increasingly on non-viral vectors, which don't carry this risk. Only specialists under rigidly controlled laboratory conditions can produce viral vectors. By contrast, the nanoparticles developed by the UB team can be synthesized easily in a matter of days by an experienced chemist.

The researchers make their nanoparticles from hybrid, organically modified silica (ORMOSIL), the structure and composition of which allow for the development of an extensive library of tailored nanoparticles to target gene therapies for different tissues and cell types.

A key advantage of the team's nanoparticle is its surface functionality, which allows it to be targeted to specific cells. While they are easier and faster to produce, non-viral vectors typically suffer from very low expression and efficacy rates, especially in vivo. According to the researchers, this is the first time that a non-viral vector has demonstrated efficacy in vivo at levels comparable to a viral vector.

In the experiments, targeted dopamine neurons -- which degenerate in Parkinson's disease, for example -- took up and expressed a fluorescent marker gene, demonstrating the ability of nanoparticle technology to deliver effectively genes to specific types of cells in the brain. Using a new optical fiber in vivo imaging technique, the researchers were able to observe the brain cells expressing genes without having to sacrifice the animal.

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